This invention relates to apparatus for measuring tremor in a part of a living body, for example in a limb or part of a limb of a human body.
Tremor is a series of involuntary, small variable movements involving a part or parts of the body moved by skeletal muscles. Limb tremor can be divided into two categories, namely normal and abnormal tremor, and these can be sub-divided into rest tremor, postural tremor and intention tremor. Rest tremor occurs when a limb is hanging freely without voluntary movement, and is commonly increased in diseases involving the extrapyramidal system, for example Parkinson's disease. Intention tremor occurs when a limb is voluntarily moved from one position to another, and is increased in diseases where there is a degeneration of the cerebellum and basal ganglia, for example multiple sclerosis, Parkinson's disease and Wilson's disease. Postural or physiologic tremor occurs when a limb is voluntarily maintained in a position rather than rest. Abnormal postural tremor occurs during withdrawal from addiction to alcohol or drugs such as narcotics and barbiturates. Normal postural tremor is increased during fatigue, anxiety and stress. Also, normal postural tremor is reduced by alcohol, and hence may provide an involuntary measure of the effect of alcohol.
For various reasons, some of which will be evident from the proceeding paragraph, the measure of tremor is extremely useful in the treatment of various diseases or other abnormal conditions of the human body. Because of the actual physical movements involved in tremor, i.e. very small rapid movements of widely differing amplitude and frequency, the reliable measurement of tremor and the interpretation of the results of such measurements present considerable problems. To be of practical use, apparatus for the measurement of tremor should not only measure tremor accurately but should also present the results of such measurements in a manner which can be relatively easily interpreted by medical personnel. Known apparatus of this kind has not fulfilled both these requirements.